There isn't really a demo version per-se; however, you can cruise on over to
http://webmail.patternet.com and log in to your IMAP (not POP3) server.
This is an easy setup. If you need help, you can IM me, or PM me, or almost anyone on the board (or post a topic) or read the forums on installation for help.
You can try on your own. If you run into snags, that's what we're here for. If you want someone to do it for you, I'm sure someone could help you set it up (or do it for you).
Of course people help!! You just have to ask!!
This is completely free. The script is completely free. You can download it, modify it as you see fit. No royalties to pay of any kind.